Card feeders have been used in conjunction with receiving devices, such as printers or plastic laminators, for many years. A conventional card feeder has a card holder, acting like a storage stack, for holding a stack of cards to be fed into the receiving device attached to the card feeder for further processing of the cards. The card holder is positioned within the card feeder to form a chamber for storing the cards. The depth of the chamber varies depending on how many cards are stored in the card feeder. Moreover, the commercially available cards on the market are predominantly rectangular shaped and are made of paper or plastic materials. Therefore, to ensure every card is in line with other cards of the card stack for a proper feeding position, the card holder is typically of rectangular shape and is slightly larger than the size of a conventional business card.
The conventional card feeder has an opening to allow the cards to be removed from the card feeder. The opening of the card feeder may be on the top, or at the bottom, of the card holder depending on the configuration of the receiving device coupled to the card feeder. A feeding mechanism contacts, or is positioned in close proximity to, the card stack to retrieve the cards through the opening of the card feeder. To ensure proper operation of the receiving device, the feeding mechanism retrieves only one card each time from the card stack. Otherwise, if two or more cards were fed into the printer simultaneously, a blank card might be attached to a printed card coming out of the printer, or they may jam the printer and/or the card feeder. Therefore, the feeding mechanism and the card feeder have to be carefully designed to ensure only one card is retrieved at a time.
The card holder ordinarily has a platform at the bottom to uphold the card stack. To properly feed a card into the receiving device, such as a printer, the cards in the card holder have to be tightly packed, but not so tight as to cause any difficulty in removing the cards by the feeding mechanism. In addition, there should be no gap between any two cards or between the bottommost card and the platform. Otherwise, the feeding mechanism might not be able to properly remove the cards from the card feeder. To remove a card from the stack, the feeding mechanism also has to be suitably designed to overcome friction on either side of the card to be removed. The removing force of the feeding mechanism, thus, depends on how strong the friction is to be overcome during the removal of the cards. For any feeding mechanism, the removing force needed depends on the configuration of the card feeder and is substantially constant and predetermined once manufactured.
For a bottom card feeder, i.e., the opening for removing the cards is at the bottom of the card feeder, the accumulative weight of the card stack causes proper alignment of the cards to be fed. Since each card, except the bottommost card, is on top of other card(s), the weight of all other card(s) above that card will urge that card to lie evenly without gaps against an underlying card. As a result, the bottommost card will be positioned properly and is ready to be retrieved by the feeding mechanism.
The conventional bottom card feeder, however, has a major drawback, i.e., the accumulative weight of the card stack relative to each card in the stack is nonlinear. As a result, the bottommost card of the card stack will experience a much stronger accumulative weight relative to the uppermost card, which experiences no weight at all. Since the friction experienced by each card of the stack is a function to the weight, the friction experienced by each card of the stack is thus nonlinear also. As mentioned, the removing force of the feeding mechanism is substantially constant once manufactured and cannot be self-adjusted according to the variation of friction when the card stack moves from full to empty. The feeding mechanism, therefore, faces a dilemma, i.e., it has to be powerful enough to remove the bottommost card of a full stack and, at the same time, it has to be gentle enough to remove the uppermost card of an empty stack. The level of the removing force of the feeding mechanism thus has to be chosen carefully. If the feeding mechanism removes the card too forcefully, it will possibly cause some problems to the receiving device and/or the card feeder when it feeds the card into the receiving device. On the other hand, if the removing force of the feeding mechanism is not strong enough, it cannot retrieve some cards from the card stack. This causes some difficulties for a manufacturer to provide a proper level of removing force of the feeding mechanism.
To avoid the above-mentioned problems, some manufacturers provide top card feeders, i.e., feeding the cards from the top of the card holder, to the receiving devices. For a conventional top card feeder, the cards are fed into an attached receiving device through the top of the card holder. In contrast to the bottom card feeder, the uppermost card in a conventional top card feeder will be the first card to be removed from the card stack. Since there is no accumulative weight over a then uppermost card waiting for removal, every card in the stack in the top card feeder experiences substantially constant frictions, as compared to the bottom card feeder, during the removal of that card. A manufacturer of the feeding mechanism, therefore, has few problems choosing a proper level of removing force.
The conventional top card feeders are, however, not without disadvantages. Typically, a conventional top card feeder has a spring as a counterweight to pull or push up a card holder having a stack of cards positioned thereon. The conventional top card feeder has fixed surrounding walls forming a chamber to store the card stack. To load the card stack into the card feeder, a user will have to push down on the card holder to create space for loading the card stack. The user thus normally has to use both hands, one for pushing down and holding the card holder and one for holding and loading the cards, to load the card stack into the conventional top card feeder. This is inconvenient and it often causes trouble during loading. For example, the user's hands are, in most cases, larger than the cards to be loaded in the card feeder. It is, therefore, difficult to put hands into the card feeder in order to push and hold the card holder for loading. Also, if the user does not hold the card holder firmly during loading, the card holder will likely bounce back and mess up the orderly placed card stack, and it will possibly hurt the hands of the user.